ARAS Eruptive Stars Information Letter #17 | 2015-07-19| 1 / 52 ARAS Eruptive Stars Information letter n° 17 #2015-05 19-07-2015 ARAS Web page http://www.astrosurf.com/aras/ ARAS Forum http://www.spectro-aras.com/forum/ ARAS list https://groups.yahoo.com/neo/groups/sp ectro-l/info ARAS preliminary data base http://www.astrosurf.com/aras/Aras_Data Base/DataBase.htm ARAS BeAM http://arasbeam.free.fr/?lang=en ARAS Spectroscopy Contents Observations of May-June 2015 Authors : F. Teyssier, S. Shore, P. Berardi, F. Boubault, T. Bohlsen, D. Boyd, C. Buil, P. Dubreuil, J. Edlin, P. Fosanelli, O. Garde, K. Graham, J. Guarro, D. Li, F. Mete, J. Montier, T. Lester, U. Sollecchia, P. Somogyi, E. Wiley Novae p. 2 - 13 Nova Del 2013, Nova Cyg 2014, Nova Cen 2013, In nebular phase Nova Sgr 2015b : dust formation episod Nova Oph 2015 Symbiotics p. 14 CH Cygni campaign p. 15 - 22 BF Cygni p. 23 - 25 AG Dra : short flare in may p. 26 - 28 AG Peg : an historical outburst p. 29 - 33 T CrB, TX Cvn, V443 Her, YY Her, RS Oph, CQ Dra,V624 Cas, Z And p. 34 - 42 Notes from Steve Shore : Nova Sgr 2015 No. 2 forms dust: the event and the physics p. 43 - 45 Miscellaneous The X nova and HMXB in strong outburst p. 46 A photo-ionized nebula observed around the dwarf nova PNV J03093063+2638031 p. 48 - 49 By Paolo Berardi Next issue : July 2015 Nova Sgr 2015 b forms dust So the bottom line is keep monitoring this nova spectro- scopically. It will be faint for a while, but you've all done fainter and at lower resolu- tion it will still be valuable to have the coverage. And you will be able to get an idea of what happens during the dust formation in any object, in- cluding winds, by following this event. Steve Shore
Transcript
ARAS Eruptive Stars Information Letter #17 | 2015-07-19| 1 / 52
ARAS Eruptive StarsInformation letter n° 17 #2015-05 19-07-2015
ARAS Web pagehttp://www.astrosurf.com/aras/
ARAS Forumhttp://www.spectro-aras.com/forum/
ARAS listhttps://groups.yahoo.com/neo/groups/spectro-l/info
ARAS preliminary data basehttp://www.astrosurf.com/aras/Aras_DataBase/DataBase.htm
ARAS BeAMhttp://arasbeam.free.fr/?lang=en
ARAS Spectroscopy
Contents
Observations of May-June 2015
Authors :F. Teyssier, S. Shore, P. Berardi, F. Boubault, T. Bohlsen, D. Boyd,C. Buil, P. Dubreuil, J. Edlin, P. Fosanelli, O. Garde, K. Graham,J. Guarro, D. Li, F. Mete, J. Montier, T. Lester, U. Sollecchia,P. Somogyi, E. Wiley
Novae p. 2 - 13
Nova Del 2013, Nova Cyg 2014, Nova Cen 2013,In nebular phaseNova Sgr 2015b : dust formation episodNova Oph 2015
Symbiotics p. 14
CH Cygni campaign p. 15 - 22 BF Cygni p. 23 - 25AG Dra : short flare in may p. 26 - 28AG Peg : an historical outburst p. 29 - 33
T CrB, TX Cvn, V443 Her, YY Her, RS Oph,CQ Dra,V624 Cas, Z And p. 34 - 42
Notes from Steve Shore : Nova Sgr 2015 No. 2 forms dust:
the event and the physics p. 43 - 45
Miscellaneous
The X nova and HMXB in strong outburst p. 46
A photo-ionized nebula observedaround the dwarf nova PNV J03093063+2638031 p. 48 - 49By Paolo Berardi
Next issue : July 2015
Nova Sgr 2015 b forms dust
So the bottom line is keepmonitoring this nova spectro-scopically. It will be faint fora while, but you've all donefainter and at lower resolu-tion it will still be valuable tohave the coverage. And youwill be able to get an idea ofwhat happens during the dustformation in any object, in-cluding winds, by followingthis event.
Steve Shore
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NOVAE
ARAS DATA BASE : http://www.astrosurf.com/aras/Aras_DataBase/Novae.htm
Nova Del 2013 V339 DelMaximum 14-08-2013Days after maximum 594Current mag V 13.2Delta mag V 8.8
Nova Cyg 2014 V2659 CygMaximum 09-04-2014Days after maximum 356Current mag V 13.5Delta mag V 4.4
Status of current novae 1/2
Nova Cen 2013 V1369 CenMaximum 14-12-2013Days after maximum 472Current mag V 9.8Delta mag V 6.3
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NOVAE
ARAS DATA BASE : http://www.astrosurf.com/aras/Aras_DataBase/Novae.htm
Status of current novae 2/2
NovaSgr 2015Maximum 15-02-2015Days after maximum 44Current mag V 10.9Delta mag V 1.6
NovaSgr 2015 #2Maximum 21-03-2015Days after maximum 10Current mag V 5Delta mag V 0.5
Nova Oph 2015Maximum 01-04-2015Days after maximumCurrent mag VDelta mag V
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NOVAE
Nova Cyg 2014
LuminosityMag V = 13.3 (30-06-2015)Slow decline
SpectroscopyNova Cyg in nebular phase
Jim Edlin obtained a spectrum late june with his 24”CDK and a LISA at R = 1000.The FWHM of [OIII] lines is ~ 1050 km.s-1Note the strong [OII] blend 7319, 7325H alpha is deformed in its red edge by [NII] 6583
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NOVAE
ARAS Data Base : 26 spectra : http://www.astrosurf.com/aras/Aras_DataBase/Novae/Nova-Oph-2015.htm
Coordinates (2000.0)
R.A. 17 29 13.5
Dec. - 18 46 12
Nova Oph 2015 (PNV J17291350-1846120)
The AAVSO light curve from 30th of march to 30th of june, 2015Spectra of ARAS database : brown points
Last spectrum in ARAS data base obtainedby Terry Bohlsen (R = 1400)The nova enters nebular phase. See noticea-bly [OIII] increasing slowly
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NOVAE
Coordinates (2000.0)
R.A. 13 54 47.0
Dec. -59 09 08.0
Nova Cen 2013 (PNV J17291350-1846120)
V1369 Cen evolves slowly innebular phaseThe profile of H alpha line isstongly deformed by [NII]6548, 6583
AAVSO light curve since 2013, december
Comparison ofH beta[OIII] 5007 (intensity x 1/20)[OIII] 4363
Note the strong differencebetween [OIII] 5007 and4363 (saddle shape)
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NOVAE
Nova Sgr 2015b
AAVSO light curve (V band)ARAS Spectra : blue dots
Coordinates (2000.0)
R.A. 18 36 56.8
Dec. -28 55 39.8
After two months of oscilla-tion, the nova has undergonea formation of dust event(ATel 7299).The luminosity declined ofmore than 5 magnitude injune.Fe II remains strong duringthis transition phase.The high luminosity of thisnova allows ARAS observersto follow this nova during thedust event.See Steve’s notes page 43-45
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NOVAE
Nova Sgr 2015b Evolution in May and June, 2015 throw low resolution spectra
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NOVAE
Nova Sgr 2015b Evolution in May and June, 2015 throw low resolution spectra
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NOVAE
Nova Sgr 2015b
Eshel spectrumby Olivier Garde,just at the beginning
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NOVAE
Nova Sgr 2015b
Ha Hb Hg
EShel spectrum at R = 11000by C. BuilDuring the dust formationevent
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NOVAE
Nova Sgr 2015b
Evolution of Nova Sgr 2015 b
EShel spectra
Blue : O. Garde 2015-06-03Red : C Buil 2015-06-17Green : C Buil 2015-06-17
H alpha
[O I] 6300 [N II] 5755
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ARAS DATA BASE | http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics.htm
Symbiotics
Mag V * : 01-04-2014
Observing
CH Cygni campaignEspecially high resolution H alphaCH Cygni remains at a high level ofactivity.
BF Cygni
AG Dra : short flare detected inJune
AG Peg : historical outburst
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ARAS DATA BASE | http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics/CHCyg.htm
CH Cygni campaignSymbiotics
Coordinates (2000.0)
R.A. 19 24 33.0
Dec. +50 14 29.1
AAVSO V band light curve from march to june, 2015CH Cyg remains in high state with a flickering of about 0.3-0.4 mag - In June, appears a slowly decreasing trendARAS observations : blue dots
CH Cygni ARAS campaign : see page 22 and previous issues
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CH Cygni campaignSymbiotics
Various profiles of H alpha lineR = 11000 to 15000
V < R V > R
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CH Cygni campaignSymbiotics
An example of time seriesDong Li Lhires III 2400 l/mmR = 1500010 mns between each spectrumTotal duration = 1 hour
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CH Cygni campaignSymbiotics
A runwith no significativechange ; just littlechange of V/R ratioJacques MontierLhires III 2400 l/mmR = 15000180 s betweeneach spectrumTotal duration = 45mns
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CH Cygni campaignSymbiotics
Blue/Green Region by Palolo Berardi LHIRES III R = 4000
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CH Cygni campaignSymbiotics
4549.47 Fe II (38) + 4549.62 Ti II (82) , 4555.89 Fe II (37), 4558.66 Cr II (44), 4563.76 Ti II (50)(According to Hack & al. 1988)
CH Cygni observed at R = 50000 by Christian Buil
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ARAS Data Base for CH Cygnihttp://www.astrosurf.com/aras/Aras_DataBase/Symbiotics/CHCyg.htm
CH Cygni
Coordinates (2000.0)
R.A. 19 24 33
Dec. +54 14 29.1
Current magnitude V = 7.4 to 7.6(Flickering)
Field of CH Cygni - Christian Buil - 15-03-2012
Reference stars
Name RA (2000) Dec (20002) Sp. Type Mag. V EB-V
HD 192640 20:14:31.9 +36:48:22.7 A2V 4.96 0.026
Name RA (2000) Dec (20002) Sp. Type Mag. V EB-V
HD 183534 19:27:42 +52:19:14 A1V 5.7 0
MILES Standart for high resolution spectra
Reference for low resolution spectra
Observing
High resolution spectraEshelLHIRES III 2400 l/mm ( H alpha)Spectra should be corrected for heliocentric velocity
Low resolution spectra (minimum R = 600)With an excellent correction of atmospheric/intrumental response for computation of the SED
Send spectraTo francoismathieu.teyssier at bbox.fr
File name : _chcygni_aaaammdd_hhh.fitAnd _chcygni_aaaammdd_hhh.zip for eShel and Time series
Request for observations of the symbiotic star CH Cygni (Dr A. Skopal)Symbiotics
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BF CygniSymbiotics
Coordinates (2000.0)
R.A. 19 23 53.5
Dec. +29 40 29.2
Slowly decliningThe hump in the red part of Halpha remains strongChanges in the blue absorption
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BF CygniSymbiotics
Coordinates (2000.0)
R.A. 19 23 53.5
Dec. +29 40 29.2
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BF CygniSymbiotics
Coordinates (2000.0)
R.A. 19 23 53.5
Dec. +29 40 29.2
Tim Lester detected a significative change inthe blue absorption of H alpha line
Spectra : T. Lester at R = 9000
Evolution of H alpha line,Especially blue absorption fromapril to june 2015Spectra at R = 9000 to 12000T. LesterP. SomogyiDong LiF. Teyssier
2015-04-01.3052015-06-03.269
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AG Dra : short flare late maySymbiotics
Coordinates (2000.0)
R.A. 16 01 41.0
Dec. +66 48 10.1
Mag V 9.7
The symbiotic binary and super-soft X-ray source AG Dra is going into outburstATel #7582; U. Munari (INAF Padova-Asiago), G. L. Righetti, U. Sollecchia, F. Castellani (ANS Collaboration)on 1 Jun 2015; 10:49 UT
The yellow symbiotic binary and luminous super-soft X-ray source AG Dra is on a steep rise in optical brightness, after seven years offlat quiescence following the 2006-08 multi-maxima outburst episode (Munari et al. 2009, PASP 121, 1070). We are tightly monitoringAG Dra both photometrically and spectroscopically with various ANS Collaboration telescopes and the Asiago 1.22m and 1.82mtelescopes. On March 8.923 UT, when the current brightening begun, we measured B=11.301, V=9.885, Rc=9.005, and Ic=8.367, whileour last measurement on May 29.883 UT provides B=10.989, V=9.683, Rc=8.822, and Ic=8.228. The start of what looks like as a newoutburst episode is marked by a significant lowering of the usually very high ionization conditions: the HeII 4686 / Hbeta ratio hasdeclined from 0.83 in Nov 2014 to 0.67 on May 29.86 UT, and the ratio between OVI Raman scattering at 6830, 7088 and HeI 6678,7065 has lowered from 3.80 to 1.58. The profiles of emission lines are still broadly similar to those of quiescence, in particular no P-Cygabsorption has yet appeared.
AG Dra is a yellow symbiotic binary, with an orbital period of 550 days and a pulsation one of 355 days (Galis et al. 1999, A&A 348,533). The high galactic latitude, large radial velocity (-135 km/s) and low metallicity of the K giant donor star ([Fe/H]=-1.3, Smith et al.1996, A&A 315, 179), point to a partnership of AG Dra with the Galactic Halo. The luminous super-soft X-ray emission was discoveredby ROSAT (Greiner et al. 1997, A&A 322, 576). AG Dra went through 3 major outburst periods during the last 50 years, in 1980-82,1994-96 and 2006-08, each showing multiple maxima. These maxima have either been of the "cool" (probably related to an expansionand cooling of the white dwarf photosphere, with decline/disappearance of high ionization features) and of the "hot" type (probablycaused by an enhancement in the wind from the white dwarf, with no reduction in the ionization degree; Gonzalez-Riestra et al. 1999,A&A 347, 478; Skopal et al. 2009, A&A 507, 1531; Shore et al. 2010, A&A 510, A70). During previous outbursts, the X-ray and theoptical/UV brightness have been anti-correlated.
Late May, the yellow symbioticAG Dra showed a short flare in Vband. The Luminosity raised frommag V = 9.7 (19/05) to V = 9.5(23/05) and returned promptly toMag 9.7 (31/05).
Munari & al. deduced an outburstfrom this rise (see Atel #7582).But, during former outbursts(2006-2008), AG Dra reached aluminosity of about 8 in V band.
AAVSO light curve for 2015ARAS spectra (may-june) : brown points
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AG DraSymbiotics
AG Dra just after the flare by D. Boyd (LISA R = 1000, flux calibrated spectrum)
H alpha line at R= 15000(Lhires III - 2400 l/mm)
05-05-2015 : P. Somogyi25-05-2015 : Dong Li29-05-2015 : P. Somogyi
No significant change during(25-05) and after the flare(29-05)
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AG DraSymbiotics
He I 6678, 7065 and Raman OVI 6830, 7085 by Paolo Berardi (Lhires III - 1200 l/mm) at R = 6000A few days after the flare
The H alpha region by Tim Lester (Home made spectrograph R = 9000)
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ARAS DATA BASE | http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics.htm
AG Peg in outburst : an historical eventSymbiotics
Coordinates (2000.0)
R.A. 19 23 53.5
Dec. +29 40 29.2
AG Peg has been detected in outburstSee : http://www.aavso.org/aavso-alert-notice-521This is the first symbiotic outburst of this star.The luminosity in V band began to rise afterthe 25th of may.
AG Peg in outburst by Christian Rives (LISA R = 1000)
A low res spectrum of the nova taken just yesterday evening by a S:A 200 and a Celestron8 working at f 5:20x 5 sec images 12 A/ pix dispersion. Calibration for the response by thetheta Pegasi spectrum in Vspec. Evident H Balmer serie in emission and He II.Fulvio Mete
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AG PegSymbiotics
Comparison of low state (2014-12-25) and outburst spectra (2015-06-30)
The changes in the spectre are typical of a symbiotic outburst, produced by the expansion of thehydrogen burning envelop at the surface of the white dwarf. The envelop reacts to expansion bycooling. The peak of luminosity is shifted to longer wavelenghts, which produces the raise of lu-minosity in visible range.The TiO bands weakens, overhelmed by the Balmer continuum.The decrease of the temperature leads to the decline of ionization state : the high excitation linesweakens, such as [Fe VII] or Raman OVI. Note the enhancement of low ionisation lines for in-stance He I 4922, 5016.
Blue : 2014-12-25.778 F. Teyssier LISA R = 1000Red : 2015-06-30.044 D. Boyd LISA R = 1000
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AG PegSymbiotics
The blue/green region by Tim Lester (R = 9000)
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AG PegSymbiotics
H alpha profile by Dong Li,P. Somogyi and J. Montier.The first spectrum is ob-tained the 12th of june, dur-ing the rise.No significant change of theprofile at date.
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AG PegSymbiotics
The symbiotic nova AG Peg was shining at ~9 magwhen in 1850 started the outburst that in 1871reached a peak brightness of ~6 mag. The very slowrise to maximum was followed by an even slower de-cline that took longer than a century to complete. Thestar was at m(vis)=7.6 in 1943, at m(vis)=8.1 in 1963,m(vis)=8.5 in 1983, and declined to m(vis)=8.75 by2003.(In Atel 5258, Munari & al., 2013)
The nova outburst of AG Peg(Adapted from Kenyon, 2001)
A model for A PegIn Kenyon & al., 1993
The historical light curve (V + Vis) from AAVSO data base (since 1941)Showing the slow decline of the nova outburst, periodic orbital variations and thecurrent outburst)
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ARAS DATA BASE | http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics.htm
T CrBSymbiotics
Coordinates (2000.0)
R.A. 15 59 30.16
Dec. +25 55 12.6
Mag 10.2
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ARAS DATA BASE | http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics.htm
T CrBSymbiotics
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ARAS DATA BASE | http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics.htm
TX CVnSymbiotics
Coordinates (2000.0)
R.A. 12 44 42.0
Dec. +36 45 50.6
Mag V 9.8
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ARAS DATA BASE | http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics.htm
RS OphSymbiotics
Coordinates (2000.0)
R.A. 17 50 13.2
Dec. -06 42 28
Mag V
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CQ DraSymbiotics
Coordinates (2000.0)
R.A. 12 30 06,6
Dec. +69 12 04
Mag V 12
http://adsabs.harvard.edu/abs/2003MNRAS.346..855W
A new symbiotic in the database.
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RS Oph, Z And, V627 CasSymbiotics
Interesting results of H alphalines at high resolution byPeter Somogyi and Dong LiSee also Spectra of
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CI CygSymbiotics
Coordinates (2000.0)
R.A. 19 50 11.8
Dec. +35 41 03.0
Mag V 11
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ARAS DATA BASE | http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics/V443Her.htm
V443 HerSymbiotics
Coordinates (2000.0)
R.A. 18 22 08.4
Dec. +23 27 20.0
Mag V ~11.4
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ARAS DATA BASE | http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics.htm
YY HerSymbiotics
Coordinates (2000.0)
R.A. 18 14 34.2
Dec. +20 59 21.3
Mag V 12.8
YY Her is a faint classical symbiotic (mag V ~13)
R = 9000 R = 12000
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Nova Sgr 2015 No. 2 forms dust:the event and the physicsSteve Shore 1/4
You will likely all have heard by now that the awaitedevent -- the formation of a dust envelope in theejecta of nova Sgr 2015 no. 2 -- began about oneweek ago (around Jun 17-19) and has almost reachedits minimum. This i only the second time in the lastthirty years that such an event has been seen pan-chromatically, the last time being V705 Cas 1993.
Observations are ongoing with Swift in X-rays (usingthe XRT) and in the ultraviolet and optical (usingUVOT) but with one great addition. This time thereare also low resolution spectra (R ~ 1000, not farfrom Alpy) covering 1600-6000 Å with the grismmounted on the UVOT. Supporting UV photometryis being obtained in several broadband filters but thatis secondary to the spectroscopy. At the start of theobservations, the source was bright enough that thestrongest emission in the optical and the windows inthe UV were saturated but now that the flux hasdropped almost a factor of 10 (as of this writing) thespectra are all well exposed and taken with a cadenceof several days to cover as far as possible the dustevent. This is far better than the archival coverage ofV705 Cas.
But to put this in context , let me explain one morepiece of the physics that was missing in the earlier,more breathless discussion of the dust formingevent. As the ejecta expand, the equilibrium temper-ature of the material drops. That is a hard way ofsaying that th flux being constant (almost) from thecentral star, the radiation becomes more ``dilute'' intime and the kinetic energy density in the ejectadecreases with time so the ejecta cool. Even if thereis still only a minor radiative loss from the gas, colli-sions producing emission lines in an optically thinmedium rob the kinetic energy of the gas particles toexcite the emission that then escapes from the ejec-ta. The combined effects of this cooling is that ifthere is any attractive interaction among the gasparticles, for instance a neutral interaction caused bythe dipole-dipole (mutual polarizability) attraction(this is also called the van der Waals force), the at-
oms can coalesce to form small clusters. This isanother way of saying they form large molecules.These grow from sticky collisions until they become,in essence, so large with so many possible modes ofvibration that they are really little solids. At this pointthey are {\it grains}. The stability of these then de-pends only on the total energy and there is a criticaltemperature below which they are stable, called theDebye temperature, that depends on the density ofthe solid (not its volume) and the internal soundspeed (rather, the acoustic velocity for a compres-sion, similar to what you'd get in a seismic distur-bance in a macroscopic sample). When the energy inthe different vibrational modes of the crystal areequally distributed, the matter is at the Debye tem-perature. It's another way of saying the solid(crystal,m grain) vibrates but doesn't rupture. Whenthe temperature that balances the photon heatingwith radiative cooling of the grain reaches or fallsbelow this temperature, the solid is stable. This doesnot guarantee that the cluster will form, no less grow,but it means that once a cluster has formed it willremain without evaporating or shattering. Note,importantly, that this is not a function of ambientdensity, just the rate at which the mods of the crystalare excited because it is warm.
Now two things can happen and we do not knowwhich is dominant, if either. In a simple condensa-tion process, small nuclei grow (like droplets inclouds) around condensation nuclei (that come froma thermally unstable medium that starts to formblobs) and the instability causes progressively m,oreof these to appear rapidly as the preferred state ofthe gas shifts from the atomic or small molecular toclusters and hierarchical clusters. In symbiotic stars,those of the so-called D-type, the winds form dustsomewhere and this drives the mass loss and alsoproduces a characteristic emission signature in theinfrared (more on that in a moment). The alternatescenario is that as the UV becomes more transpar-ent, if there is a weak ionizing continuum (above afew eV), then the gas becomes partly ionized and can
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induce dipole interactions that are both faster andmore efficient than the vn der Waals and the clustersgrow by literally attracting particles.
What we know from the UV observations of Sgr 2015no. 2 is that the UV is becoming stronger, the Fecurtain is lifting, and the ejecta is showing emissionfrom atomic ions (e.g. C II). The successive wavs ofbrightenings that we discussed a while back, mightstill be happening but they're being obscured by thedust. The critical temperature is about 1000-1500 Kand this is reached (with the observed expansionvelocity of the nova) in about 70-90 days (dependingon the geometry the observed maximum velocity isalways an underestimate). If the ejecta are too opti-cally thin, the matter will become ionized rapidly andthis inhibits the coagulation by either mechanism. If,on th other hand, the ionization is too low the nucle-ation may not be rapid enough to form a thick shell.The observed UV spectrum indicates that a sort ofopaque screen is falling over the lines, blocking yourview as an external observer but not affecting thincident radiation on the ejecta from the central star,so the most distant matter is where the dust appearsto be forming. As it obscures the ejecta, there isanother clue to the location of formation. Imaginethis is not only in the periphery but throughout theejecta. Then, since dust is a continuum absorber (notlines, as in a wind), the receding parts of the ejectaare more absorbed than the approaching if the dustis uniformly forming or forms mainly in the innerejecta. On the contrary, if dust forms mainly in theperiphery then the two sides are roughly equallyextinguished. The former produces blueshifted emis-sion (the red side disappears) while the latter produc-es a more uniform change. So even low resolutionspectra can detect the difference. In supernovae,you see this asymmetric effect. In novae, it seems wedon't but this is the ideal test case (even in theoptical).
Now to continue with the energy budget, consider agrain that absorbs a fraction of the incident light. Itisn't just absorbing a line, whatever radiation is inci-dent can be absorbed with an efficiency that depends
on the grain composition. Think of a typical mineral.It has a broadlband color but seen spectroscopicallyhas broad bands rather than single lines. This is aneffect of the solid, the mutual interaction betweenthe constituent atoms in a lattice or matrix of thesolid is so strong that the levels broaden out intobands. So for an incident flux at some wavelength l Fl, some fraction is scattered (reflected) -- the frac-tion called the wavelength dependent albedo, Al -and some absorbed 1 - Al. So the total amount of
energy absorbed is the product (1 - Al) Fl p a2. Thelast factor is the geometric projected area of thegrain of radius a summed over all possible wave-lengths of the incident light. The grain continues toheat until the rate of emission balances that of ab-sorption since the emission rate increases as thetemperature rises. The farther the grain is from thecentral source, the lower the incident flux (recall thatthe flux varies as 1/d2 with distance d) so the totalenergy emitted produces a progressively lower tem-perature for the grain as d increases. Since the cen-tral source, and inner ejecta that shields theperiphery, is always hotter than the grains, and thegrain temperature must be below the critical value,the grains will emit in the infrared and the totalemission depends only on the amount of dust that'sformed and not on the grain size. I apologize if this isgetting heavy again but you all asked for this. Therise of the infrared is, consequently, the signature ofdust formation if it is accompanied by a drop in theUV and optical and the total of excess and deficitshould be approximately zero if the ejecta complete-ly cover the central source along the line of sight to adistant observer (i.e. you). This is precisely what wasseen for V705 Cas, and inferred for such novae as DQHer 1934 for which dust formation was first hypothe-sized to explain the deep extended minimum in theoptical light curve (long before UV observations andsatellites).
Solids, because they also scatter light, act as mirrors(albedo again). But they are irregular and not neces-sarily uniformly distributed. You know that polaroidsunglasses work best in reducing the intensity of
Nova Sgr 2015 No. 2 forms dust:the event and the physicsSteve Shore 2/4
ARAS Eruptive Stars Information Letter #17 | 2015-07-19| 45 / 52
reflected light because, like scattering, it is polarized.So polarization is a signature of the solid, since ther-mal emission is incoherent and unpolarized. For themoment, the Liverpool Robotic Telescope is offline,Murphy's Law strikes again, but there are others whowill be getting such photometric (and spectrophoto-metric) measurements during this event and its re-covery. As the expansion thins out the ejecta, theoptical depth of the dust drops so eventually theinfrared emission remains but the optical an UV re-cover as you can see through the ejecta again to theinner parts and the central star, so the decline re-turns to its regularly scheduled rate. We should seethis in a few months, the duration of the deep mini-mum depends on the ejecta mass and maximumexpansion velocity. None of this happens in a wind,in which the dust forms at some distance throughwhich the matter continually flows.
Perhaps the most spectacular consequence of dustformation in these beasts is that you can actually pickup a piece of the ejecta to study it. More precisely,the grains are expelled into the interstellar mediumwhere they drift along with all other dust from all thevarious stellar sources (e.g.l red giant and supergiantwinds, supernova explosions) but have distinctivecompositions because of the nuclear processing inthe TNR stage of the explosion (about which therehave already been some notes some time ago).Because the nuclear processing leading to the explo-sion favors the production of proton rich isotopes(like 15O and 13N) and also continues into the Si and Srange, there are very distinctive isotopic patternsthat are come from novae and no other known Galac-tic sources. These grains, when mixed into the othergarbage, become part of the star formation processand, in protostellar disks, solidify and grow into plan-etesimals and meteoritic parent bodies. OK, they arerare but they stand out in any sample and, in meteor-ites, there is a small population of so-called pre-solargrains that actually show the Si and S isotopic ratiospredicted for novae. I mean very few, but in meteor-
ites like Murchison (a fall in Australia in 1969, part ofwhich is on display in the US at the National Museumof Natural History) some of these grains have beenrecovered (seehttp://home.dtm.ciw.edu/users/lrn/preprints/nittler-omeg07.pdfhttp://arxiv.org/pdf/astro-ph/0405332.pdfhttps://journals.uair.arizona.edu/index.php/maps/article/viewFile/15454/15442
This is one of the very few times you can think thatthere are components of you that were also formedin nova explosions and dispersed in the grains thatcome from this relatively rare class.
So the bottom line is keep monitoring this nova spec-troscopically. It will be faint for a while, but you've alldone fainter and at lower resolution it will still bevaluable to have the coverage. And you will be ableto get an idea of what happens during the dust for-mation in any object, including winds, by followingthis event.
Steve Shore,25-06-2015
Nova Sgr 2015 No. 2 forms dust:the event and the physicsSteve Shore 3/4
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V404 Cyg
The X-ray nova and LMXB (low mass x-ray binary) V404Cyg undergone a bright outburst in june.See for instancehttp://www.astronomerstelegram.org/?read=7659For a description of the spectrum
Paolo Berardi and Peter Somogyi obtained two spectraof this rare event ; a challeging target
The AAVSO light curve of the outburstshowing the strong oscillations during all the phenomenon
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Nova Sgr 2015 No. 2 forms dust:the event and the physicsSteve Shore 4/4
AG Dra, observed with SwiftA brief notice. Observations with Swift, both grism (UV and optical) and XRT (X-rays) around mid-May came upempty. There are no detectable X-rays but since the source was weak for XMM-Newton and ROSAT, this isn't agreat surprise. More interesting is the comparison of a single STIS/HST sequence from 2013 Aug and the latestSwift grism spectra. The flux levels are virtually the same, within about 10-15\%, as they were through most of hespectrum but not between 2000 and 2500\AA. This may be a poor calibration (this is a known problem, as is thesecond order contribution to the spectrum) or it may be real. The mid-UV is brighter by about 20\% than it hadbeen while the boundary portions remain identical. I don't know many mechanisms that could do this and notleave other spectral signatures, e.g. Fe emission lines, but it's possible that this is a flux excess. Rather thanimplying a temperature, it's likely indicating a change in opacity. Observations have been temporarily haltedbecause of the activity of both N Sgr 2015 no.2 and V404 Cyg, a black hole binary (period of about one week, similarto several other systems such as Cug X-3) that has gone into its first outburst since 1989 (it's produced a flood ofATel communications but worth reading). This is almost an SS 433 type system so it would be worth a lowresolution try (Alpy, for instance).
V1369 Cen, V339 Del
Just a quick note. Observations were taken of V1369 Cen with FEROS at ESO and HST/STIS a week ago and of V339 Delfrom NOT and HST/Swift about a month ago. Both are clearly in the deep nebular stage post-supersoft turnoff. Butwhat is quite unexpected and (I think) lovely is that the V1369 Cen profiles on UV lines are completely different thanthe FEROS optical data. The two (see figure) show some features in common but few. But this may indicate animportant measurements, almost by chance: the small aperture was used for the UV, with a side of 0.2 arcsec. In theoptical, a 1. arcsec fiber was used. The profiles fit a narrow cone or individual filaments in the UV while the largeroptical fiber would have covered the source completely. So it looks like the ejecta are resolved spatially and thisimplies a distance of 2-3 kpc (to produce a size of 0.4 arcsec, about twice the UV small aperture). The comparison isstriking when you compare a permitted recombination line, e.g. He II 1640\AA, and a forbidden line with about thesame ionization potential (optical, [O III] 5007 Å). The V339 Del status is a continuing decline, the ejecta are nowrecombining slowly without further ionization from the central source, hence the expansion is controlling everything.The density continues to follow the same law for ballistic expansion we discussed and there's no indication that theejecta are resolved. The UV absorption lines are definitely present, Si IV 1400, C IV 1550, N V 1240 Å, with velocitiesthat have not changed during these months. But to say why is another question, and it's best to leave that for the nextnewsletter.
V 1369 Cen - 2015 June, 6In optical (ESO/FEROS) and UVHST/STIS
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The optical transient PNVJ03093063+2638031 wasobserved by ARAS spectro-scopists shortly after its dis-covery occurred on 29October 2014. Our spectrahave revealed that the objectis a dwarf nova in outburst(ref. CBAT TOCP). Time re-solved photometry confirmedthe WZ Sge type on the de-tection of early superhumps(VSNET).
We took several spectra atlow (R~1000) and medium(R~6000) resolution, from 30october to 2 november. ThePNV faded very quickly,bringing it beyond the reachof amateur telescopes in afew days.
Recently, on 30 June 2015, Astronomy & Astro-physics published an interesting article by U.Munari et al. concerning the discovery of a photo-ionized spatially resolved nebula around the star:http://arxiv.org/abs/1506.08526Briefly, in some long-slit spectra taken at AsiagoObservatory - Italy, the hydrogen Balmer emis-sion lines showed features spatially extendingmore than the stellar continuum. The presence ofa spherical nebula around the star was deducedfrom the analysis of East-West and North-Southslit aligned spectra. There is a clear physicalassociation to the dwarf nova because it hasbeen observed that the nebula expanded overtime and turned invisible when the superoutbursthas ended (recombination completed). Further-more, there is no hint of the nebula in the historicred Palomar Sky Survey plates taken duringquiescence phases.
The nebula is also appreciable in the mid-resspectra taken with Lhires III and C9.25 on 1stand 2nd november. From the 1st november two-dimensional spectrum I tried to measure theangular size along the slit axis (E-W oriented).
The spatial FWHM (vertical profile) of H-alphaline comprising the nebula is about 11 pixels (8.1arcsec). To find the effective size we have toconsider the enlargement due to the atmosphericturbulence and small guiding errors. For thisreason the stellar continuum FWHM is 7 pixels(5.2 arcsec). Under the assumption of Gaussianprofiles, the corrected nebula FWHM along theslit axis should be approximately 6 arcsec. Thisis only an estimate also because of poor SNR ofThe nebula spectrum and relatively small focallength (and aperture) of the telescope.
A photo-ionized nebulaobserved around the dwarf nova PNV J03093063+2638031
Paolo Berardi 1/2
I found the "Y scale" of 2d spectrum equal to 0.74 arcsec/pixel. Thisis derived from the length of the slit expressed in arcsec, in turn ob-tained by measuring its length on the sky (inset: guide camera field
ARAS Eruptive Stars Information Letter #17 | 2015-07-19| 49 / 52
The spectral width of H-alpha emission is verynarrow, comparable to the instrumental FWHM,and the line centered at the same wavelengthalong its vertical extension. This indicates thatthe gas is not fast expanding or rotating.The A&A article reports that the detection of anebula around a WZ Sge star is probably aunique feature. It is suggested to search forsimilar nebulae around the same type of objectsthat will be observed in the future. This requireslong slit spectrographs. Hopefully it will be apossibile field of research also for amateurs.
Paolo Berardi,
Paolo Berardi25-06-2015
A photo-ionized nebulaobserved around the dwarf nova PNV J03093063+2638031
Paolo Berardi 2/2
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Recent publications
Novae
Early optical spectra of nova V1369 Cen show presence of LithiumL. Izzo, M. Della Valle, E. Mason, F. Matteucci, D. Romano, L. Pasquini, L.Vanzi, A. Jordan, J. M. Fernandez, P. Bluhm, R. Brahm, N. Espinoza, R. Williamshttp://arxiv.org/pdf/1506.08048v1.pdf
The Distance to Nova V959 Mon from VLA ImagingLinford, J. D.; Ribeiro, V. A. R. M.; Chomiuk, L.; Nelson, T.; Sokoloski, J. L.; Rupen, M. P.; Mukai, K.; O’Brien, T. J.; Mioduszewski, A. J.; Weston, J.The Astrophysical Journal, Volume 805, Issue 2, article id. 136, 12 pp. (2015)http://arxiv.org/abs/1503.03899
The slow decline of the Galactic recurrent novae T Pyxidis, IM Normae, and CI AquilaeCaleo, Andrea; Shore, Steven N.Monthly Notices of the Royal Astronomical Society, Volume 449, Issue 1, p.25-33http://arxiv.org/abs/1502.06763
OGLE Atlas of Classical Novae I. Galactic Bulge ObjectsP. Mroz, A. Udalski, R. Poleski, I. Soszynski, M. K. Szymanski, G. Pietrzynski, L. Wyrzykowski, K. Ulaczyk, S. Kozlowski, P. Pietrukowicz, J. Skowronhttp://arxiv.org/abs/1504.08224
Photoionization Heating of Nova Ejecta by the Post-outburst Supersoft SourceCunningham, Timothy; Wolf, William M.; Bildsten, Larshttp://arxiv.org/abs/1501.05690
SALT observations of southern post-novaeT. Tomov, E. Swierczynski, M. Mikolajewski, K. Ilkiewiczhttp://arxiv.org/abs/1502.03462
The Curious Case of ASAS J174600-2321.3: an Eclipsing Symbiotic Nova in Outburst?Stefan Huemmerich, Sebastian Otero, Patrick Tisserand, Klaus BernhardJAAVSO Volume 43,2015http://www.aavso.org/sites/default/files/jaavso/ej295.pdf
Periods in a 87 Years Light Curve of the Symbiotic Star MWC 560Elia M. Leibowitz, Liliana Formigginihttp://arxiv.org/abs/1506.05584
Symbiotic stars in X-rays III: long term variabilityN. E. Nuñez, T. Nelson, K. Mukai, J. L. Sokoloski, G. J. M. Lunahttp://arxiv.org/abs/1505.00633
Accretion Flow and Disparate Profiles of Raman Scattered O VI λλ1032, 1038 in the Symbiotic Star V1016 CygniHeo, Jeong-Eun; Lee, Hee-WonJournal of the Korean Astronomical Society, vol. 48, no. 2, pp. 105-112http://jkas.kas.org/journals/2015v48n2/v48n2p105_hwlee.pdf
The first symbiotic stars from the LAMOST surveyJiao Li, Joanna Mikołajewska, Xue‐Fei Chen, A‐Li Luo, Alberto Rebassa‐Mansergas, Yonghui Hou, Yuefei Wang, Yue Wu, Ming Yang, Yong Zhang, Zhan‐Wen Hanhttp://arxiv.org/abs/1505.06569
ARAS Eruptive Stars Information Letter #17 | 2015-07-19| 51 / 52
Recent publications
Formation of Dust in Nova Sgr 2015b
ATel #7643; Frederick M. Walter (Stony Brook University)
The bright nova N Sgr 2015b (PNV J18365700-2855420) is fading rapidly at optical wavelengths as reported in, forexample, VSNet-alert 18731 and AAVSO Alert notice 519. Observations with the SMARTS/Andicam dual-channelphotometer on the SMARTS/CTIO 1.3m telescope show a simultaneous brightening at long wavelength. From MJD57173.8 through MJD 57187.9 the V magnitude faded by 2.0 mag; J faded by 0.92 mag; the Ks magnitude brightenedby 0.25 mag. This is likely due to the formation of dust on the line of sight. The dust appears to be optically thick atleast through the J-band.
The nova remains bright with V=7.9 and K=4.5 on MJD 57187.9 (2015 June 14 UT). The near-IR magnitudes are suspectbecause core of the image is currently saturated at H, and in the non-linear part of the response at K, and are besttreated as lower limits.
We urge observers with near-IR spectroscopic capability and with near-IR and mid-IR cameras to monitor the forma-tion of the dust.
Meanwhile, we continue to monitor this nova photometrically in BVRIJHK and spectroscopically with the Chironechelle at R=78,000. There are prominent absorption systems in H-beta, Fe II 517 nm, and Na D at velocities of -700,-800, -1600, and -1800 km/s. Details of the line profiles change nightly, but no gross changes in line profiles seem tocoincide with the dust formation.
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Please :- respect the procedure- check your spectra BEFORE sending themResolution should be at least R = 500For new transcients, supernovae and poorly observed objects,SA spectra at R = 100 are welcomed
1/ reduce your data into BeSS file format2/ name your file with: _novadel2013_yyyymmdd_hhh_Observer novadel2013: name of the nova, fixed for this object
Exemple: _chcyg_20130802_886_toto.fit
3/ send you spectra to Novae, Symbiotics : François Teyssier Supernovae : Christian Builto be included in the ARAS database
Submit your spectra
Contribution to ARAS data baseFrom 01-05 to 30-06-2015
About ARAS initiativeAstronomical Ring for Access to Spectroscopy (ARAS) is an informal group of volunteers whoaim to promote cooperation between professional and amateur astronomers in the field ofspectroscopy.
To this end, ARAS has prepared the following roadmap:
• Identify centers of interest for spectroscopic observation which could lead to useful, effec-tive and motivating cooperation between professional and amateur astronomers.• Help develop the tools required to transform this cooperation into action (i.e. by publishingspectrograph building plans, organizing group purchasing to reduce costs, developing andvalidating observation protocols, managing a data base, identifying available resources inprofessional observatories (hardware, observation time), etc.•Develop an awareness and education policy for amateur astronomers through trainingsessions, the organization of pro/am seminars, by publishing documents (web pages), manag-ing a forum, etc.• Encourage observers to use the spectrographs available in mission observatories and pro-mote collaboration between experts, particularly variable star experts.• Create a global observation network.
By decoding what light says to us, spectroscopy is the most productive field in astronomy. It isnow entering the amateur world, enabling amateurs to open the doors of astrophysics. Whynot join us and be one of the pioneers!
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